1. Field of the Invention
The present invention relates to a symbol color compensating technology for a color display system such as a television set, and more particularly, to an improved symbol color compensating method for a color display system wherein a color density and brightness are controlled on the basis of one selected from a variety of image colors being displayable on the color display system.
2. Description of the Background Art
In order to reproduce symbol colors using a color processing image system such as a TV or a monitor, it is important to reproduce a flesh tone, a blue color and a green color for reproduction and evaluation of colors since the flesh tone, blue and green colors are recognized by viewers as significant remembrance colors. The flesh tone has its value as a reference color, the blue color is related to a three-stimulus value and the green color is a color must sensitive to the human visual sense.
Proposals have been made to detect and compensate particular colors in such color display systems as TVs and monitors. One of them is to adjust demodulation the axes of R-Y and B-Y signals. This is to adjust the magnitude of a relative vector value of the colors with regard to color demodulation axes, wherein the flesh tone is set as a reference color among a variety of symbol colors so that the demodulation axes are moved toward the reference color by as much as a predetermined phase angle. However, this method has disadvantage in that all the reproduced colors are concurrently changed without regard to the existence of the reference color in the image-received frame when a image is received in a TV in real time. Further, the relative vector value is decreased with regard to the demodulation axes, thereby disadvantageously deteriorating the color density in the reproduced image.
In order to overcome such drawbacks, there was introduced a method for detecting a particular symbol color from the slope of the color-modulated value by use of R-Y and B-Y values received from a microcomputer in the display system. Under the present NTSC mode, the R-Y and B-Y values are appropriately combined on the basis of the R-Y and B-Y values of the color demodulation axes, for thereby reproducing the colors transmitted to a color image display device. For that purpose, a maximal value and a minimal value are obtained with regard to the R-Y and B-Y values while changing respective phase angles of flesh tone, blue and green experimentally by as much as xc2x110% from the reference phase.
FIG. 1 is a graph illustrating a color phase distribution of flesh tone, blue and green with regard to demodulated color values, wherein the horizontal axis denotes B-Y values and the vertical axis denotes R-Y values. The shaded portions represent a flesh tone region, a blue region, and a green region.
According to the experimental result, as shown in FIG. 1, the minimal and maximal B-Y values for the flesh tone are 3.283 and 3.395, and the minimal and maximal R-Y values for the flesh tone are 3.868 and 2.922. The minimal and maximal R-Y values for green are 3.554 and 3.641. The minimal and maximal B-Y values for blue are 2.492 and 2.532. The minimal and maximal R-Y values for blue are 3.112 and 3.273.
In order to detect symbol colors on the basis of the demodulated values, with regard to flesh tone, blue and green, the following method is employed.
First, 3.1 is subtracted from the R-Y, B-Y values inputted in the microprocessor, respectively. Secondly, the respective slopes of the B-Y and R-Y values are obtained. Thirdly, the respective colors corresponding to the inputted values on the basis of the obtained slope values are sorted into one of the flesh tone, blue and green. In other words, if the R-Y and B-Y values of the inputted values belong to the shaded portions in FIG. 1, the inputted values are respectively assigned to flesh tone, blue and green; otherwise, the inputted values are assigned to the original colors.
However, such a conventional method also has a disadvantage in that an additional parameter must be provided to accurately detect the symbol colors.
The present invention is directed to overcoming the conventional disadvantages.
Therefore, it is an object of the present invention to provide a symbol color compensating method for a color display system wherein the symbol colors are compensated by a method using flesh tone, blue and green which serve as reference colors and wherein the three colors are important for color reproduction and color evaluation.
It is another object of the present invention to provide a symbol color compensating method for a color display system wherein the symbol colors are reproduced without influencing the colors other than flesh tone, blue and green.
To achieve the above-described object, there is provided a symbol color compensating method for a color display system according to the present invention which includes the steps of detecting colors of a plurality of pixels from an image being displayed, calculating an entire frequency number of flesh tone, blue and green colors from the detected colors, selecting one color of the flesh tone, blue and green colors when the calculated frequency number is more than a predetermined value, and controlling a color density and a brightness value in accordance with the selected color.
The objects and advantages of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.